Integrated circuit having a reduced spacing between a bus and adjacent circuitry

ABSTRACT

An integrated circuit that reduces spacing between circuitry and a bus. In accordance with this invention, the bus is a strip of conductive material in a layer of the integrated circuit. The layer includes at least one slot that removes conductive material from the bus. The removal of the conductive material in the slot allows the space between circuitry adjacent the bus and the bus to be reduced.

CROSS-RELATED

This application is a utility application claiming priority to anearlier filed U.S. Provisional Application No. 60/323,574 filed Sep. 19,2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to integrated circuits. More,particularly, this invention relates to reducing spacing between a busand adjacent circuits. Still more particularly, this invention relatesto defining slots in the bus during design of an integrated circuit toreduce the space needed between the bus and adjacent circuitry.

2. The Prior Art

As the electrical arts advance, the amount of circuitry in an integratedcircuit is increasing. Therefore, it is a problem for those that designintegrated circuits to maximize the space in an integrated circuit wherecircuitry can be placed.

Currently, designers of integrated circuits are limited by the spacingrequirements between a bus and circuits that are adjacent to the bus inthe integrated circuit. For purposes of this discussion, a bus is astrip or line of conductive material which carries signals betweencircuits and a circuit is any configuration of circuitry that is in theintegrated circuit. Also, for purposes of this discussion, conductivematerial is a metal or other type of substance having properties thatallow transmission of electric signals.

The present design process requires a designer to place a solid strip ofconductive material in a layer of the integrated circuit. The designermust then use the properties of the solid strip of conductive materialto determine the spacing between the strip and a circuit that isadjacent to the strip. The designer then places the circuit adjacent tothe bus with the determined amount of spacing separating the circuitfrom the bus.

FIG. 1 illustrates the above-described configuration. In layer 100 of anintegrated circuit, a bus 101 is a solid strip of conductive material.Circuit 102 and circuit 103 are adjacent to bus 101 on opposite sides ofbus 101. Circuit 102 and circuit 103 are both separated by distance D,represented by arrows 104 and 105, from bus 101. Distance D isdetermined from the width of bus 101. The width of bus 101 is used todetermine the density of the conductive material in bus 101 whichdictates the distance D of separation that must be maintained by the busand an adjacent circuit.

After the circuit is designed with the bus made of a solid strip ofconductive material. The design is provided to the manufacturer. Themanufacturer then cuts slots into the strip of conductive material ofthe bus. The slots remove conductive material to change the density ofconductive material in the bus and make the bus more manufacturable.

FIG. 2 illustrates a layer 200 of integrated circuit after the routingis completed in the manufacturing process. In layer 200, bus 100 is astrip of conductive material that has slots 201 in the strip. Each slot201 is devoid of conductive material. The slots change the amount ofconductive material in the strip, which in turn changes the density ofthe material. However, the distance, D, between the bus and adjacentcircuits 102,103 has not been changed. Therefore, circuits 102 and 103are further away from the bus than is needed.

BRIEF DESCRIPTION OF THE INVENTION

This patent discloses and claims a useful, novel, and unobviousinvention for an integrated circuit with reduced separation between abus and adjacent circuits. In accordance this invention, slots are putinto a strip of conductive material of a bus to reduce the amount ofconductive material in the bus. The addition of the slots is performedduring the design of the integrated circuit as opposed to during a postdesign step.

The addition of the slots into the strip of conductive material of thebus during the design process offers many advantages. A first advantageis that since the final density of conductive material in the bus isknown at design time, the spacing between the bus and adjacent circuitsmaybe reduced. A second advantage is that since the position of theslots is known to the designer at design time, a designer may avoidplacing connectors to other circuits over slots causing a disconnect.

In accordance with the present invention a layer of an integratedcircuit has a first circuit in the layer and a bus in the layer. The busis adjacent to the first circuit. The bus is a strip of conductivematerial with at least one slot defined in the strip. The slot removesconductive material from the strip to allow a reduction of spacingbetween the bus and the first circuit. The other configurations of thisintegrated circuit are described below.

In order to provide the integrated circuit described above, anintegrated circuit is designed in the following manner. First, a stripof conductive material acting as a bus is placed in a first layer of theintegrated circuit. Slots are then defined in the conductive material ofthe strip to remove conductive material in the strip. The spacingbetween the bus and an adjacent circuit is then determined from theamount of conductive material in the strip after the slots have beenmade. A circuit is then placed adjacent to the bus with the amount ofseparation determined by the amount of conductive material in the strip.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The above and other advantage and features in accordance with thisinvention are described in the detailed description and shown in thefollowing drawings:

FIG. 1 illustrating a diagram of a prior art layer of an integratedcircuit after the design process;

FIG. 2 illustrating a diagram of a prior art layer of an integratedcircuit after processing by a manufacturer;

FIG. 3 illustrating a diagram of a layer of an integrated circuit inconfigured in accordance with this invention;

FIG. 4 illustrating a flow diagram of a process for designing anintegrated circuit in accordance with this invention;

FIG. 5 illustrating a flow diagram for a process of placing a bus in alayer of an integrated circuit and defining slots in the bus inaccordance with this invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description of embodiments of this invention is notintended to limit the scope of the invention to the shown embodiments,but rather to enable any person skilled in the art of to make and usethis invention.

FIG. 3 illustrates a layer 300 of an integrated circuit configured inaccordance with this invention. Layer 300 includes busses 301-304. Eachof busses 301-304 may be a signal bus for transmitting electricalcurrent between circuits or may be a power bus for supplying electricalcurrent to a circuit. One skilled in the art will recognize that thetype of bus does not matter as the concepts of this invention may beapplied to any type of bus.

Each of busses 301-304 has at least one circuit 310-312 adjacent atleast one side of the bus. One skilled in the art will recognize thatexact configuration or function of each circuit 310-312 is not essentialto understanding this invention and has been omitted for brevity. Eachof the buses 301-304 is a strip of conductive material in layer 300. Ina preferred embodiment, conductive material is a metal, such as copper.However, one skilled in the art will recognize that other metals orother conductive materials may be used. Each bus also has at least oneslot 351-355 in the bus. Each slot is an area where the conductivematerial of the strip has been removed. The removal of the conductivematerial changes the amount of material in the strip of each of thebusses 301-304. Thus, the density of conductive material in each bus isreduced. One skilled in the art will recognize that the change indensity of the conductive material changes impedance of the material.This in turn changes the amount of space required between a circuit andthe bus in order to prevent the current on the bus from interfering withcurrent flowing through the circuit. One skilled in the art willrecognize that there are many commonly available methods and equationsfor determining the impedance of the conductive material that arecommonly available in various text books and other related materials.This allows the distances, D, of areas 320-325 between circuits 310-312and adjacent ones of busses 301-304 to be reduced.

The determination of the spacing between a side of one the busses301-304 and an adjacent circuit is calculated from the density or amountof conductive material in the bus. Typically, there are design ruleswhich are well known in the art which govern the minimal distance neededbetween the bus and adjacent circuitry based upon the density ofconductive material in the bus.

Bus 303 is now described in detail. One skilled in the art willrecognize that other bus 301,302 and 304 are configured in the samemanner and descriptions of each are omitted for brevity. Bus 303 has afirst center strip 330 of conductive material in first layer 300. Secondstrip 331 of conductive material is adjacent first center strip 330 on afirst side of first center strip 330. Second strip 331 is substantiallyparallel to first center strip 330.

Cross connect strips 341-345 connect first center strip 330 and secondstrip 331. Preferably, cross connect strips 341-345 are substantiallyperpendicular to first center strip 330 and second strip 331. Crossconnect strips 341-345 are also preferably substantially parallel to oneanother. Furthermore, cross connect strips 341-345 are also preferablyspaced evenly apart from one another.

Slots 353 are defined by cross connect strips 341-345. Slots 353 are thespaces between adjacent cross connect strips 341-345, the first side offirst center strip 330 and the side of second strip 331 opposing thefirst side of first center strip 330. Preferably, slots 353 are spaceevenly apart from one another by cross connect strips 341-345. Slots 353are also preferably have the same area as one another. Each slot 353also is an area of non-conductive material such as the material used asthe substrate for first layer 300.

In addition to second strip 331, a third strip 332 may be placed infirst layer 300 on a second side of first center strip 330 which isopposite of the first side of first center strip 330. Third strip 332 isadjacent first center strip 330 and substantially parallel to firstcenter strip 330.

Cross connect strips 346-350 connect first center strip 330 and thirdstrip 332. Preferably, cross connect strip 346-350 are substantiallyperpendicular to first center strip 330 and third strip 332. Crossconnect strips 346-350 are also preferably substantially parallel to oneanother. Cross connect strips 346-350 are also preferably spaced evenlyapart from one another. Furthermore, each cross connect strip 346-350also connects third strip 332 to first center strip 330 at the samepoint a corresponding cross connect strip 341-345 connects second strip331 to first center strip 330. Those skilled in the art will recognizethat this gives bus 343 a flip-flop and abutting configuration. Oneskilled in the art will also recognize that any additional number ofbusses may be connected in a flip flop and abutting manner using anouter strip, such as strips 331-332 shown, as the center strip.

Slots 354 are defined by cross connect strips 346-350. Slots 354 are thespaces between adjacent cross connect strips 346-350, the second side offirst center strip 330 and the side of second strip 332 opposing thefirst side of first center strip 330. Preferably, slots 354 are spaceevenly apart from one another by cross connect strips 346-350. Slots 354are also preferably have the same area as one another. Furthermore, eachslot 354 is at the same point along first center strip 330 as acorresponding one of slots 353 on the other side of first center strip330. Each slot 354 also is an area of non-conductive material such asthe material used as the substrate for first layer 300.

A signal source (Not shown) is connected to bus 303. The signal sourceis connected via a connector that connects to conductive material in thebus and not a slot where there is no conductive material. Preferably,each of strips 330-332 is connected to the signal source. The signalsource may be on first layer 300 or on a second layer of the integratedcircuit. One skilled in the art will recognize that the signal sourcemay be a power supply or a circuit that generates a signal.

FIG. 4 is a flow chart of a process 400 for designing an integratedcircuit in accordance with this invention. One skilled in the art willrecognize that the order that the steps of process 400 are completed maybe changed without diverting from concepts of this invention. Oneskilled in the art will also recognize that this process relates toplacing a bus and circuitry onto a layer of an integrated circuit anddoes not include the steps of designing and laying out the components ofa circuit.

Process 400 begins in step 405 with placing a bus in the first layer.The width of the bus may vary depending on the amount of current thatthe bus needs to carry. A preferred method for placing the bus in thefirst layer is given in process 500 of FIG. 5. In step 406, at least oneslot is defined in the bus. The number and size of the slot slots may bedetermined by the amount of conductive material that is needed in thebus for resistance and current requirements of the bus. A preferredprocess for defining the slots is also shown in FIG. 5.

In step 407, the amount of spacing needed between the bus and adjacentcircuitry to ensure proper functioning is determined. The amount ofspacing required is determined by density of the conductive material inthe bus. Alternatively, the amount of spacing is determined from theamount of conductive material in the bus. In a preferred embodiment,there is a set of rules that provides the amount of spacing needed basedupon the conductive material in the bus. Alternatively, the spacing maybe calculated.

In step 408, a first circuit is placed adjacent to the bus on a firstside of the bus. The space calculated in step 407 is used to separatethe first circuit from the bus. In step 409, a second circuit is placedadjacent to the bus on a second side of the bus opposite of the firstside. The space calculated in step 407 is used to separate the secondcircuit from the bus.

In step 410, the signal source is connected to the bus. As stated above,the signal source is connected to the bus in a position along the bushaving conductive material and not in an area of a slot. Also, thesignal source may be connected to each strip in the bus as describedabove. After the signal source is connected, the design may be providedto a manufacturer or other post design user in step 411. Then, process400 ends.

FIG. 5 illustrates a preferred process 500 for providing the bus anddefining the slots for steps 405 and 406 of process 400. Process 500begins in step 505 by placing a first strip of conductive material inthe first layer. In step 510, a second strip of conductive material isthen placed in the first layer adjacent to the first strip on a firstside of the first strip. The second strip is preferably substantiallyparallel to the first strip.

In step 520, a third strip of conductive material is then placed in thefirst layer adjacent to the first strip on a second side of the firststrip adjacent opposite of the first side. The third strip is preferablysubstantially parallel to the first strip.

In step 520, a third strip of conductive material is then placed in thefirst layer adjacent to the first strip on a second side of the firststrip adjacent opposite of the first side. The third strip is preferablysubstantially parallel to the first strip.

In step 525, cross connect strips are placed in the first layer toconnect the first strip to the third strip. The cross connect strips arepreferably placed even distances apart from one another. This definesslots that have substantially equal distance from one another. The crossconnect strips also have substantially equal widths that provide uniformspacing of the slots. The cross connect strips are also preferablyplaced substantially perpendicular to the first and third strips. Eachcross connect strip between the first and third strip connects the thirdstrip to the first strip at the same point along the first strip as acorresponding one of the cross connect strips between the first andsecond strips. This creates a flip-flop and abutting configuration. Oneskilled in the art will recognize any number of additional strips may beadded to the bus in a like manner using the second or third strips as afirst strip. Process 500 then ends.

As any person skilled in the art of circuit design will recognize fromthe previous description and from the figures and claims, modificationsand changes can be made to the preferred embodiments of the inventionwithout departing from the scope of the invention defined in thefollowing claims.

What is claimed is:
 1. An integrated circuit that minimizes spacingbetween circuitry comprising: a first circuit in a first layer of saidintegrated circuit; and a bus in said first layer of said integratedcircuit adjacent said first circuit wherein said bus includes a strip ofconductive material with at least one slot defined in said strip ofconductive material to remove conductive material from said strip toallow a reduction of spacing between said bus and said first circuitwherein spacing between said bus and an adjacent circuit is determinedbased upon an amount of said conductive material in said strip ofconductive material of said bus.
 2. The integrated circuit of claim 1further comprising: a second circuit in said first layer of saidintegrated circuit adjacent to said bus on a side of said bus oppositesaid first circuit wherein spacing between said bus and said secondcircuit is reduced because of said removal of conductive material insaid at least one slot.
 3. The integrated circuit of claim 1 whereinsaid bus is a power bus.
 4. The integrated circuit of claim 1 whereinsaid bus is a signal bus.
 5. The integrated circuit of claim 1 whereinsaid at least one slot defined in said strip of conductive materialcomprises a plurality of slots defined in said strip of conductivematerial.
 6. The integrated circuit of claim 5 wherein said slots areevenly spaced in said strip of conductive material.
 7. The integratedcircuit of claim 5 wherein said strip of conductive material comprises:a first strip of conductive material in said first layer; a second stripof conductive material in said first layer adjacent and substantiallyparallel to said first strip wherein said second strip is spaced apartfrom said first strip; and a first plurality of cross connect strips ofconductive material that connect said first strip and said second stripwherein a first plurality of slots are defined between said plurality ofcross connect strips.
 8. The integrated circuit of claim 7 wherein saidfirst plurality of cross connect strips are substantially perpendicularto said first strip and said second strip.
 9. The integrated circuit of7 wherein said strip of conductive material comprises: a third strip ofconductive material in said first layer that is adjacent to andsubstantially parallel to said first strip on an opposite side of saidfirst strip of power material from said second strip wherein said thirdstrip is spaced apart from said first strip; a second plurality of crossconnect strips of conductive material the connect said third strip tosaid first strip wherein a second plurality of slots are defined asspaces between adjacent ones of said second plurality of connect strips.10. The integrated circuit of claim 9 wherein said second plurality ofcross connect strips are substantially perpendicular to said first stripand said third strip.
 11. The integrated circuit of claim 9 wherein saidsecond plurality of cross connect strips are spaced evenly apart fromone another.
 12. The integrated circuit of claim 9 wherein said secondstrip and said third strip are connected to said first strip by saidfirst and second plurality of cross connect strips at common points in aflip-flop and abutting manner.
 13. The integrated circuit of claim 9further comprising: a signal source wherein said signal source isconnected to each of said first strip, said second strip, and said thirdstrip.
 14. The integrated circuit of claim 7 further comprising: asignal source wherein said signal source is connected to each of saidfirst strip and said second strip.
 15. The integrated circuit of claim 1further comprising: a signal source in second layer of said integratedcircuit; and a connector that connects said signal source to said bus ona portion of conductive material of said strip.
 16. The integratedcircuit of claim 1 wherein spacing between said bus and an adjacentcircuit is determined based upon a density of said conductive materialin said bus.
 17. A method for providing a design of an integratedcircuit that provides minimal spacing between a bus that transmitssignal and a circuitry adjacent to said bus, said method comprising:placing a bus in a first layer of an integrated circuit; defining atleast one slot in said bus to remove excess conductive material fromsaid bus to reduce spacing required between said bus and an adjacentcircuit; determining an amount of spacing between said bus and saidfirst circuit based upon an amount of conductive material in said bus;and placing a first circuit in said first layer adjacent to said bus ona first side of said bus wherein said spacing between said bus and saidfirst circuit is reduced in response to removing excess conductivematerial from said bus with said slot in said bus.
 18. The method ofclaim 17 further comprising: determining an amount of spacing betweensaid bus and said first circuit is determined based upon a density ofsaid conductive material in said bus.
 19. The method of claim 17 furthercomprising: placing a second circuit in said first layer adjacent tosaid bus on a second side of said bus opposite of said first sidewherein spacing between said bus and said second circuit is reduced inresponse to removing excess conductive material from said bus with saidslot in said bus.
 20. The method of claim 19 further comprising:determining an amount of spacing between said bus and said secondcircuit based upon an amount of conductive material in said bus.
 21. Themethod of claim 19 further comprising: determining an amount of spacingbetween said bus and said second circuit is determined based upon adensity of said conductive material in said bus.
 22. The method of claim17 wherein said step of defining said at least one slot: defining aplurality of slots in said strip of conductive material.
 23. The methodof claim 22 wherein said step of defining said plurality of slotscomprises: evenly spacing each of said plurality of slots in said stripof conductive material.
 24. The method of claim 22 wherein said step ofplacing said bus comprises: placing a first strip of conductive materialin said first layer; placing a second strip of conductive material insaid first layer adjacent and substantially parallel to said first stripwherein said second strip is spaced apart from said first strip; andconnecting said first strip and said second strip with a first pluralityof cross connect strips of conductive material in said first layerwherein a first plurality of slots are defined between said plurality ofcross connect strips.
 25. The method of claim 24 wherein said step ofplacing said bus further comprises: aligning said plurality of crossconnect strips substantially perpendicular to said first strip and saidsecond strip.
 26. The method of 24 said step of placing said bus furthercomprises: placing a third strip of conductive material in said firstlayer adjacent and substantially parallel to said first strip on anopposite side of said first strip of power material from said secondstrip wherein said third strip is spaced apart from said first strip;and connecting said third strip to said first strip with a secondplurality of cross connect strips of conductive material wherein asecond plurality of slots are defined as spaces between adjacent ones ofsaid second plurality of connect strips.
 27. The method of claim 26wherein said step of connecting said first step and said third stripcomprises: placing said second plurality of cross connect stripssubstantially perpendicular to said first strip and said third strip.28. The method of claim 26 wherein step of connecting said first stripand said third strip further comprises: spacing said second plurality ofcross connect strips evenly apart from one another.
 29. The method ofclaim 26 further comprising: connecting said second strip and said thirdstrip to said first strip by said first and second plurality of crossconnect strips at common points in a flip-flop and abutting manner. 30.The method of claim 26 further comprising: connecting a signal source toeach of said first strip, said second strip, and said third strip. 31.The method of claim 24 further comprising: connecting a signal source toeach of said first strip, and said second strip.
 32. The method of claim17 further comprising: connecting a signal source in second layer ofsaid integrated circuit in a portion of conductive material of saidstrip.
 33. The method of claim 17 further comprising: providing saiddesign of said integrated circuit to a manufacturer.